Oh, and in oxy-acetylene torches valve sequencing is as much a matter of convenience as anything. It's not possible to light oxygen on fire, so you have to have the fuel open first. You could have them both open, but then you'd torch your striker, and having a cloud of mixed oxyacetylene rapidly gets too exciting. http://www.youtube.com/watch?v=0fWBINa7cxI

On shutdown you can turn the fuel off first, but it makes an annoying pop. I usually try to turn them off near simultaneously, so as to not have those little soot strings floating around the shop that you get from a big acetylene flame.

About the only malfunction you usually get out of them is overheating the tip so that the oxyacetylene is burning inside the torch, which makes a loud popping noise. It could be vaguely compared to combustion instability in a rocket engine.